1. Field of the Invention
This invention relates to stents and a method for inserting a stent.
2. Brief Description of the Prior Art
It is desirable in various situations that means be provided for expanding a constricted vessel portion or for maintaining an open passageway through a vessel portion. Such situations arise, for example, in conjunction with the disease known as arteriosclerosis as well as the growth of a tumor so as to restrict or stop flow of blood through a blood vessel. Dr. Charles Dotter et al. reported in 1969 on the experimental use of coiled stainless steel wire stents placed in the popliteal arteries of dogs. Although the coils exhibited long-term patency, narrowing of the lumen occurred within them and only small coils could be passed percutaneously. See Dotter CT et al., Transluminally-Placed Coilspring Endoarterial Tube Grafts, Invest. Radiol., 1969; 4:329-332.sup.1. Recently, two laboratories reported on the use of a prosthesis constructed of a thermal shape memory alloy, nitinol, which is passed through a catheter. See Dotter CT et al., Transluminal Expandable Nitinol Coil Stent Grafting, Radiology, April, 1983; 147:259-260.sup.2, and Cragg A. et al., Nonsurgical Placement of Arterial Endoprostheses, Radiology, April, 1983; 147:261-263.sup.3. Such stents can be complicated to use, requiring ice water or heated saline for placement. Also they have been found to produce luminal narrowing due to fibrin deposition on the stent wires.
Other references which may have relevance to the present invention are the following U.S. patents: Sakura U.S. Pat. No. 4,214,587; Alfidi U.S. Pat. No. 3,868,956; and Simon U.S. Pat. No. 4,425,908; and the Russian Pat. No. 978,821; also the following publications: C. Gianturco et al., A new vena cava filter: experimental animal evaluation, Radiology, December, 1980; 137:835-837.sup.4 ; and M. Simon et al., A Vena Cava Filter Using Thermal Shape Memory Alloy, Diagnostic Radiology, 125:89-94, October 1977.sup.5. Still another reference publication is D. Maass et al., Radiology Follow-up of Transluminally Inserted Vascular Endoprostheses: An Experimental Study Using Expanding Sprials, Radiology, September 1984; 152:659-663.
Objects of the invention are to provide a stent which is easy to place and use that reduces flow defects, luminal narrowing and occlusion.